As is known, semiconductor materials having a wide forbidden bandgap, in particular having an energy value Eg of the forbidden band greater than 1.1 eV, low resistance in the ON state (RON), high value of thermal conductivity, high operating frequency, and high saturation value of speed of the conduction charges, are ideal for the manufacturing of electronic components, such as, for example, transistors or switches, in particular for power applications. A material having these characteristics and suitable for use in the manufacture of electronic components is silicon carbide (SiC). In particular, silicon carbide, in its different polytypes (for example, 3C—SiC, 4H—SiC, 6H—SiC), may be preferable to silicon as regards the properties listed above.
Electronic devices provided on a silicon carbide substrate, as compared to similar devices provided on a silicon substrate, may possess a plurality of advantageous characteristics, such as, for example, a low output resistance in the ON state, a low leakage current, high operating temperatures, and high operating frequencies.
Likewise well known is the fact that, in order to form integrated electronic devices in a silicon carbide substrate, it is necessary to introduce into the substrate dopant elements for generating doped regions of an N type or of a P type. For example, by implanting nitrogen (N) atoms or phosphorus (P) atoms, donors are introduced, which provide regions of an N type, whilst by implanting boron (B) atoms or aluminium (Al) atoms, acceptors are introduced, which provide regions of a P type.
A technological problem, associated with activation of the donors and of the acceptors implanted, regards the fact that any type of dopant element implanted in the silicon carbide requires a particularly high activation temperature, equal to or higher than 1800° C. A temperature that is so high can, however, damage other components or fabrication layers present on the substrate during the process of thermal activation, for example, the layers used for definition of the implanted areas, as well as the SiC substrate itself.
A possible solution to this problem is described in the patent application No. EP 1 742 271, which is incorporated by reference, and in which doped surface regions are provided by implanting in a localized way dopant elements in a 4H—SiC substrate, by means of appropriate ion implantations performed according to various angles and without using processes of thermal diffusion.
Said solution, however, may not be optimal, in so far as it requires particular arrangements for performing the process of ion implantation, such as, for example, precise angles of implantation. Finally, it may be necessary to perform, after the implantation process, a thermal-annealing step for enabling activation of the implanted elements. The optimal annealing temperature, higher than 1600° C., cannot, however, be reached on account of the presence of various layers deriving from the production process. At said temperature, in fact, the layers present on the substrate would be damaged in an irreversible way.